The present invention relates to a sublimable dye toner, a method of manufacturing a sublimable dye toner and methods of using sublimable dye toners in xerographic applications.
In U.S. Pat. No. 3,900,318 to Zographos et al., issued Aug. 19, 1975, a process is disclosed which involved the use of sublimable dispersed dyes in photoelectrophoretic image reproduction. The dispersed dyes can be converted into the vapor phase at temperatures of between 160.degree. and 220.degree. C. under atmospheric pressure. In this imaging process, the dye-containing particles themselves are the photoreceptors.
U.S. Pat. No. 4,251,611 to Mehl et al., issued Feb. 17, 1981, discloses a process for the information of a permanent image in which one or more colors from a latent electrostatic image which correspond to the color separations of an original are developed by means of a developer composed of polymer particles containing a dyestuff which can sublime or polymer particles containing a dyestuff which can sublime or vaporize at between 100.degree. and 250.degree. C. Latent images are developed on a photoconducting element by means of a developer containing, in addition to the dyestuff, a ferromagnetic substance incorporated into the polymer particles. Each image thus developed is brought into contact with a receiving sheet which possesses an affinity for the vapors of the sublimable or vaporizable dyestuff of the developers. Next, the resulting material is heated above the vaporization or sublimation temperature of the dyestuff to be transferred. These steps are carried out in the case of each latent image, until the image to be reproduced has been recomposed. This process can effectively destroy the photoreceptor and is not suitable for use in a plain paper xerographic application.
U.S. Pat. No. 4,262,078 to Ishida et al., issued on Apr. 14, 1981, discloses a light transmitting particle containing a sublimable color-former which is a pyridine derivative suitable for use in the formation of a color image. The process of Ishida et al. uses the light transmitting characteristics of the particle to form an image.
U.S. Pat. No. 4,238,562 issued to Ishida et al. on Dec. 9, 1980, discloses a light transmission particle for forming a color image. The particle contains a sublimable dye that is a spirobenzopyran indole compound suitable for use in the formation of a color image. The process disclosed in Ishida et al. is similar to that of U.S. Pat. No. 4,262,078, in that the process uses the light transmitting characteristics of the particle to form the image.
U.S. Pat. No. 4,230,784, issued to Nishiguchi et al. on Oct. 28, 1980, discloses image-forming particles for use in electrostatic image production. These particles have a light transmitting property and comprise an electrically conductive material and a subliming substance. In the process of Nishiguchi et al., an image is formed by directly exposing tile toner.
In "Fabrication of Color Filter Arrays for Solid-Stale Imagers by Laser Induced Dye Diffusion into Polymers", Journal of Imaging Science, 29(5), page 161-163, by R. O. Loutfy et al., published September/October 1985, a technique is described for fabricating color filter arrays for use in conjunction with solid-state imaging devices. The technique involves selectively heating dye samples with thermally conductive, convective, or radiative means, such as a laser. Line and spot resolutions of about 10 micrometers or less are achieved.
In "The Anatomy of Xerography" by Mort (1989), on page 133 it is stated that color toners are made by mixing an organic pigment with a toner resin by means of either a batchwise or continuous operation using high shear mixers to produce a blend of a taffylike consistency.
U.S. Pat. No. 4,124,384 to Centa, issued Nov. 7, 1978, discloses an image reproduction process is disclosed which uses a photohardenable element containing photohardenable layers toned with a toner material comprising a sublimable dye. The process involves heating the above-stated toned layer while in contact with a receptor material, therefore causing the dye to sublime imagewise and condense on the receptor material. The receptor comprises polymer organic compounds.
U.S. Pat. No. 4,456,669 to Yubakami et al., issued Jun. 26, 1984, discloses an image forming process disclosed utilizing heat-transferable dyes to form images on a receiving substrate. Image signals are used to arrange image forming particles on a support member. The particles contain a dye former which is heat-transferred onto an image receiving substrate. After heating, a color developing agent is used to adhere to the dye former to provide colored images.
U.S. Pat. No. 4,121,932 to Ishida, issued Oct. 24, 1978, discloses an electrophotographic process for forming a dye image. The process comprises an electrophotographic material containing a photoconductive layer consisting of photoconductive powders and sublimable dyes. The electrophotographic process further comprises charging a photosensitive element consisting of photoconductive particles and sublimable dyes, exposing and developing the element with acidic toners, heating the element to sublime the dyes and transferring the dye images to an accepting substrate.
A technical report by Datek, dated August, 1988, discloses a process known as "Dye Diffusion Thermal Transfer Technology" ("D2T2"). Advantages of "D2T2" writing with sublimable dye colorants include color purity and color mixing which yields near-photographic quality prints and transparencies. Disadvantages include the relatively high cost of supplies, including dye coated donor sheets and dye receptive "special" papers or transparency sheets.
The present invention achieves the high quality coloration attributes of dye sublimation marking in a xerographic imaging system. Also, in the accordance with the present invention, dye consumption can be limited to the amount required to produce the actual image, i.e., there is no dye donor sheet to discard. In addition, the dye receptor is the toner resin itself which can be fused, just as with regular xerographic toner, to truly plain paper. The proposed sublimable dye toner therefore achieves the advantages while it also avoids problems caused by the high supply costs of "D2T2" imaging.
The present invention is also an improvement over the prior art in that the sublimable dyes of the present invention form a much more uniform image than the pigments employed in prior art toners and processes. This is due to the fact that the sublimable dyes diffuse and this diffusion is relatively rapid and uniform. By contrast, the pigments of the prior art intermix by melting, a slow and relatively nonuniform process.